Digital Electricity™ vs. Digital Current™: What's the Difference?
December 12, 2022
You no longer need to choose between cost, power, and efficiency when running electrical cables; there’s a new electrical system on the rise, and a few manufacturers are already providing it.
A new edition of the National Electrical Code (NEC) was published in November 2022, and it introduced Class 4 power systems in a new article (article 726). This is the first time in over 45 years that a new class of power has been added to the code book (Class 3 was added in 1978).
In this article, we’ll discuss two providers of Class 4 power (CL4) systems: Cence, and Voltserver. We hope this article provides a better understanding of what Article 726 is, how class 4 systems work, how they might vary from system to system, and what the benefits are to implementing one in your building project. Class 4 power systems, also known as fault-managed power systems, can provide a solid, future-proof foundation for commercial buildings and larger facilities, and they aren’t as overwhelming or costly to consider as one might imagine. Let’s start with what a class 4 power system is, and where it fits into the existing electrical code in the United States (the NEC).
What is a Class 4 Power (CL4) System?
Electricians, engineers, building managers, and even homeowners have faced a common problem in the past. Running traditional AC power and wiring can be dangerous, but a low-voltage solution, like Power over Ethernet (PoE), can be very costly, and is not practical when more than 90 watts of power is needed for a single load. The good news is that there is a solution on the horizon that brings the best of both worlds together.
The National Electrical Code (NEC) added Article 726 to the 2023 edition. This addition includes a new class rating: class 4 power (CL4), also known as fault-managed power systems. This rating is applied to power systems that can safely distribute up to 450 volts of power, while using similar practices to that of low-voltage wiring installations. Electrical systems that meet these requirements, as well as monitor for specific faults (listed below, and in this other article), would be called Class 4 power systems. Traditional electrical systems that distribute AC power, and are most common in our homes and buildings, fall under the section of “wiring methods” in the NEC. The difference between this section, and the section on class ratings for electrical systems, is that class-rated electrical systems are power limited. Out of the 3 class ratings (class 1, 2, and 3), class 2 systems, such as Power over Ethernet, are used quite often because they provide suitable protection against both fire and shock hazards. Class 2 systems also only require low-voltage wiring practices, so they use less insulation, and don't require mechanical protection or conduit. Class 4 systems also only require low-voltage wiring practices, but are fault-managed instead of power limited (so they can provide far more power, safely).
Let’s take a look at what this means for the power class 4 systems can provide, using PoE as an example of a class 2 power system:
Because safety from electric shock and fire is ensured by fault-management in Class 4 power systems, they can provide at least 9 times the voltage (and therefore, power) of a PoE system. If the gauge of the cable is increased, more current can be transmitted, and thus more than 9x the power of PoE can be achieved. It is practical to see scenarios where 20-50x the amount of power can be transmitted (over 5000 watts).
But what is a fault-managed power (FMP) system?
Contrary to other class ratings for power systems in the NEC, class 4 systems are not limited by power output, they would actually be limited by the triggering of fault conditions (this technology is also known as fault-managed power or FMP). FMP is a power system that monitors for pre-defined faults and, if one is detected, the flow of power is stopped so that the delivered power to the fault and to the connected load is limited, almost instantly.
The predefined faults that a class 4 system must monitor for are:
An abnormal condition such as abnormal voltage, current, waveform, or load condition is identified in the system
A short circuit occurs
Human skin contacts energized parts
A ground-fault condition exists
An overcurrent condition exists
Intentional shorting of the line at the receiving or transmitting end to force deenergization for purposes of maintenance or repair occurs
A malfunction of the monitoring or control system occurs
The addition of a new class rating is a big deal, since (as we mentioned earlier) a new class rating hasn’t been added for over 45 years.
Two companies providing class 4 power systems:
Two companies that are prepared to provide class 4 power systems for the ever growing demand, are Voltserver (located in Rhode Island) and Cence Power (located in Ontario, Canada). The Voltserver Class 4 power system is called Digital Electricity™ (DE) and the Cence class 4 system is called Digital Current™ (or Cence HVDC). Both of these systems can deliver higher voltages at longer distances than a PoE system has ever been capable of, and they can do this while using low-voltage wiring practices. In the past, to deliver higher voltages over long distances, less flexible, thicker cabling has been necessary. Class 4 rated systems change that. Although both Digital Electricity™ and Digital Current™ provide the benefits of a class 4 power system in this way, they still have their differences. For example, they’re built differently, and use different patented technology. This article will go into more detail on the differences between these two systems, and perhaps give you a better idea of what constitutes a class 4 power system.
Full disclosure, this article is written by a technical researcher working at Cence, which means that we are no expert on Voltserver technology, and only have information that’s available in other articles and on their website. If you have any technical questions about Digital Electricity™, feel free to check out their website, or reach out to them. Now, let’s get into the article, starting with Digital Electricity™.
What is Digital Electricity™?
Reduction in line losses along structured cables
Circa Resort and Casino, the Hard Rock Stadium, GreenSeal Cannabis, and other large facilities use Digital Electricity™. It seems that Digital Electricity™ is often used for larger facilities because it seems to provide the most value to them. Digital Electricity™, and other class 4 power systems, have minimal line losses along their cables, meaning they experience less energy waste and voltage drop. We don’t need to get into the technical details right now for why this is the case, but basically what you need to know is that, the higher the voltage, the less line losses along cables. This is simply based on the formula for power. If you’d like a further explanation on why line losses occur along electrical cables, we have a video all about it.
Easy explanation of the 3 major types of line losses along transmission lines:
It’s a well-known fact in electrical engineering circles that increasing voltages, lowers current, and this is one way to reduce line losses. The real challenge has been to enable safe distribution of higher voltages in order to reduce these line losses along cables, and this is what fault managed power (FMP) systems, like Digital Electricity™ and other class 4 power systems, enable. This is also a big reason why many of the facilities that Voltserver works with are larger; it’s sometimes more beneficial for these larger facilities to implement a class 4 system because they often need longer cables, and they want to minimize line losses along these lengths of cables to efficiently distribute power to loads. Thus, class 4 power systems typically reduce operational costs for larger facilities running long lengths of cables. Aaron Reale, the RCDD and director of operations at Verda Tech (VT Group), put it like this:
But how does the Digital Electricity™ Class 4 system work? Let’s break it down.
Basically, Voltserver’s class 4 power system delivers power discretely or, as they say on their website, with packet energy transfer technology to their Digital Electricity™ receivers. Then, analog (continuous) power is delivered to loads. See below for a more full description of our understanding of how their system works.
1. Alternating current (AC) or direct current (DC) analog/continuous electricity is sent from the grid to Voltserver’s DE transmitter.
2. The transmitter converts the “analog” AC or DC power into Digital Electricity™. From our understanding, this means that the power from the grid is converted into Voltserver’s energy packets. This conversion is what enables their “packet energy transfer” power distribution.
What is packet energy transfer?
From the Digital Electricity™ transmitter, an “energy packet” is sent about 700 times per second, according to EDN. Take a look at the image below (labeled Fig.8): for three-quarters of each packet, Voltserver sends a small amount of power, then the remaining quarter of the same packet is used for Voltserver’s “safety check”. During this safety check, a message is sent back to the transmitter to confirm the packet has been properly sent and received. Because only a small amount of power is present in each packet, usually only low-voltage wiring practices are required for the Digital Electricity™ system. The power of each packet is accumulated together in the receiver, which is how loads get the power they need.
3. After the energy packets leave the transmitter, they are sent over structured cables to the Digital Electricity™ receiver.
4. In the receiver, the energy packets are accumulated so that enough power is available to power loads. The amount of power a receiver can handle, as well as the number of loads it can support, depends on the type of receiver obtained from Voltserver. You can view the different types of receivers Voltserver has by going to their website and clicking on Digital Electricity™ > Products > Digital Electricity™ Receivers.
5. The final step is that continuous/analog power is delivered to loads. This can be delivered as either AC or DC power.
Commercial buildings waste an average of 30% of energy consumed every year. The Argentum team, which has now joined Cence, founded Argentum Electronics in 2015 to reduce this waste by providing a direct current (DC) power distribution system, and additional smart technologies like sensors and digital twin software. The Cence system is called Digital Current™ (located in the Cence HVDC product), and is considered “digital” because it also has built-in fault management, and its high-speed digital control makes it intelligent. Like Digital Electricity™, Digital Current™ is also a Class 4 power system. It provides up to 450 Volts DC, has no wattage limit, and only requires low-voltage wiring practices.
It’s a little difficult to differentiate between Voltserver and Cence Power's ideal applications from the outside, but based on their marketing, Voltserver has poised itself to work best with larger facilities, as well as within specific industries (like telecommunications and indoor agriculture). On the other hand, the Cence mission is to provide an easy-to-install, Class 4 DC power distribution system that can improve the energy efficiency of LED lighting and HVAC systems. Applications would be most commercial, multi-family residential, and industrial buildings, and implementation would reduce energy consumption in DC powered applications by up to 40%.
Both Cence and Voltserver provide higher-voltage systems (that reduce line losses along cables), as well as DC power distribution, which eliminates the need for inefficient conversions from AC to DC power at the load level.
Eliminates inefficient AC to DC conversions
As per mentioned above, distributing DC power throughout a building eliminates AC to DC conversions at the load level. Individual conversions at the load level are usually very inefficient, wasting about 5% - 20% of energy consumed by a load. The Digital Current™ system eliminates these conversions with an included product, which connects directly to a building’s electrical panel, and makes one, highly-efficient (usually about 95%) conversion from AC to DC. Then, this DC power is distributed throughout a building, to DC powered loads. The AC powered loads in a building are unaffected by this, they are simply not connected to the Digital Current™ system.
How does the Digital Current™ Class 4 system work?
The Cence Class 4 system (Digital Current™) can be installed in both retrofits and new building projects, and, similarly to Digital Electricity™, it also includes a transmitter and receiver. Rather than delivering power discretely with electrical pulses, Digital Current™ delivers DC power continuously along cables to the receiver, and then to the load. Safety checks are performed simultaneously between the transmitter and receiver, making it a fault-managed power system. Although Digital Current™ doesn’t deliver packets of energy (like the Digital Electricity™ system), it is still a digital system because it intelligently monitors and manages power flow for faults.
Here’s how Digital Current™ works:
1. The transmitter converts power from AC to DC, and also includes an integrated safety computer. The safety features of this computer have two layers. Firstly, the onboard computer continuously monitors the power cables for faults based on the defined safety parameters. I listed the safety parameters that a class 4 system such as this one would monitor for above. For example, “human skin contacts energized parts” is one. So, if this fault occurs, power would be shut off immediately. This brings up another question: how does one ensure that the monitoring system is working properly? That’s where the second layer to the system comes in. The second layer continuously monitors to ensure that the primary safety functionality is working properly. If it’s not, this is also considered a fault, and power is shut off.
2. Next, up to 450 Volts DC power is sent continuously (rather than discretely) along cables that abide by low-voltage wiring practices.
3. When power arrives at the receiver, the receiver confirms with the transmitter that power is safe to send to loads. Additionally, the receiver senses the power requirements of the load it’s connected to, and steps down power accordingly as necessary.
4. DC power is sent to connected loads.
An Intelligent Electrical System
As we mentioned before when discussing the Cence case studies, the Cence system extends beyond electrical distribution. It also includes internet of things (IoT) technologies such as wireless sensors and digital twin software. So, let’s take this explanation of how the Cence system works a little further. Let’s say you’re an electrical engineer looking for a solution for a client to make their building as energy efficient as possible. Implementing a class 4 system can save on cabling costs, as well as eliminate inefficient AC to DC conversions, and losses along cables. So let’s say you choose to implement one as part of the project. But the client is also experiencing temperature inconsistencies throughout their building, is unsure of the air quality in their space, and wants to save energy by automating lighting and HVAC systems based on room occupancy and other desired parameters. A solution to the client’s problem could involve the implementation of various wireless sensors, along with a digital twin of the building to monitor, control, and automate both BACnet systems (ex. Lighting and HVAC) and non-BACnet systems and devices alike. More specifically, occupancy sensors can be used to monitor whether or not a space is vacant, as well as how many people are in a space. Additionally, IEQ and IAQ sensors can be used to monitor parameters that are essential to optimizing the indoor environmental quality of a space, such as: temperature, humidity, CO2 levels, the colour temperature of lighting, brightness and more. When data is collected about these things, and analyzed properly, it can be used to automate lighting and HVAC systems based on data, and optimize energy consumption in this way. In fact, when HVAC is automated based on occupancy (this is called demand controlled ventilation), HVAC energy costs are reduced by about 10% to 40%. A digital twin is a digital representation of a physical object or space. So, when we say the Cence system includes digital twin software, this means you would be able to control your building essentially through an interactive digital floor plan. See the image below. To sum up, the combination of intelligent technologies like these, along with a class 4 system, is a well-rounded solution to improve the electrical efficiency of a building.
Here's a video of a digital twin in action:
The Voltserver and Cence Class 4 power distribution systems are both solving a long-standing challenge in the world of electrical engineering; when choosing an electrical system, one shouldn’t have to choose between cost, power and efficiency. Class 4 systems provide all three of these benefits thanks to their ability to manage and limit power based on detected faults. The purpose of this article has not been to pit two companies against one another, but to explain what each of their solutions involves, and how both Digital Electricity™ and Digital Current™ work (in a nutshell).
The primary difference between the two is that Digital Electricity™ delivers power discretely in energy packets (that have built-in safety checks), and Cence delivers power continuously while simultaneous safety checks are performed between the transmitter and receiver. Regardless of the class 4 system that you choose (if you do decide that it’s right for your building), we hope to see the proliferation of class 4 systems in buildings, as they provide a solid foundation for buildings of the future.
Fun fact: Commercial buildings consume 35% of electricity consumed in the U.S, and generate 16% of all U.S. carbon dioxide emissions, according to America’s Department of Energy. Thus, reducing energy wasted by commercial buildings can make a significant impact on reducing our carbon footprint as a whole, especially when DC power distribution saves about 20% of energy wasted by DC powered electrical loads. As a power distribution system that distributes DC power (as well as AC power if necessary), Class 4 power systems could make a big difference for the architectural engineering and construction (AEC) industry.
Erin is the Creative Director at Cence Power. She has a New Media degree from the University of Toronto and 5 years of experience in the communications field. She has also done digital content creation for dozens of clients through her own business called Story Unlocked. Erin loves technology, especially when it makes the world a better place.
Cence Brings Buildings Into The Future
We improve the value of commercial and multifamily buildings with an intelligent DC power distribution system that's pain-free to install. It combines the benefits of low-voltage wiring practices with voltage capabilities of up to 450 Volts DC.